This circuit with TTL compatible output was found in a 1968 US documentation. The circuit is powered by 5 V and the frequency can be changed by changing the crystal.
This is a VU-meter bargraph with up to 7 LEDs according the Power supply voltage. Adjusts are made by...
This circuit was suggested by General Electric in 1970 documentation. It makes use of a photo-SCR...
This circuit was obtained from a 90s Elektor Electronics f. The output current of each sector is 1...